Light-emitting Diodes (LEDs) are semiconductor devices that convert electricity into ultraviolet light or visible light using characteristics of compound semiconductors so as to enable transmission/reception of signals, or that are used as a light source.
Group III-V nitride semiconductors are in the spotlight as core materials of light-emitting devices such as, for example, LEDs or Laser Diodes (LDs) due to physical and chemical characteristics thereof.
Such LEDs or LDs do not include environmentally harmful materials such as mercury (Hg) that are used in conventional lighting appliances such as, for example, fluorescent lamps and incandescent bulbs, and thus are very eco-friendly, and have several advantages such as, for example, long lifespan and low power consumption. As such, conventional light sources are being rapidly replaced with LEDs.
In particular, the application range of these light-emitting devices is broadening to encompass various fields including, for example, headlights for vehicles or flashlights. As such, light-emitting apparatuses that include light-emitting devices need to have excellent light extraction efficiency, and the demand for small size, light weight, and low manufacturing costs is also continuously increasing.